[Python-Dev] iterzip() (original) (raw)

Guido van Rossum guido@python.org
Mon, 29 Apr 2002 17:07:23 -0400

A fixed threshold of any size will leave us vulnerable to quadratic-time cases. Proportional growth wouldn't, though. For example, if a round of gc didn't find anything to collect, or found very little, we could boost the threshold by 25% (that's a right shift by 2 and an add ). Contrarily, when gc finds lots of stuff to collect, reduce the threshold. This adjusts itself to a program's runtime characteristics. I suspect most long-running programs enjoy vast stretches of time over which the second derivative of their gc behavior is relatively constant .

Should we worry about programs that don't create any cyclical garbage for a long time, and then sudenly start creating lots of it? The initial GC-free period may bump the threshold up very far, and then it will build up a significant pile of cyclical garbage before GC runs again.

--Guido van Rossum (home page: http://www.python.org/~guido/)